721 FXUS66 KPQR 312134 AFDPQR Area Forecast Discussion National Weather Service Portland OR 234 PM PDT Wed Aug 31 2016 .SYNOPSIS...A modest cold front will move through southwest Washington and northwest Oregon this afternoon and early evening, bringing cool temperatures and some light rain or showers to much of the forecast area. Another stronger disturbance or front is expected to bring more rain to the area later Thursday and Thursday evening, followed by more showers the remainder of Thursday night and Friday, with possibly even a few thunderstorms Friday. A few isolated showers may linger into the weekend. Another system is possible from the northwest early next week. Temps will be below normal most of the period. && .SHORT TERM...(Tonight through Saturday)...A modest front was moving through southwest Washington and northwest Oregon this afternoon, and will move east of the Cascades later this evening, bringing some light rain or light showers to much of the forecast area and suppressing temperatures below normal especially inland. After the front moves east of the Cascades later this evening, there will be some trailing residual showers tonight and early Thursday, especially around the higher terrain in the north part of the forecast area. The models then all focus in on a stronger disturbance rotating around the main low off the B.C. coast which breaks off the system out near 150w and develops into another front that moves into the forecast area later Thursday and Thursday evening. The models suggest QPFs from this feature could reach a quarter to a half inch or better along the coast and in the mountains, highest north, with a tenth to a quarter or possibly even a third of and inch in the valleys. After this front moves through Thursday evening, the trailing showers continue through Friday in westerly flow behind the front. The models show enough cooler air aloft sagging south for a few thunderstorms along the coast Thursday night spreading inland Friday in the northern parts of the forecast area. May start to see a little snow in the higher elevations of the Cascades by Friday. Northwest flow aloft continues Friday night and Saturday with another couple of embedded disturbances that could bring a few showers to the north part of the forecast area, especially over the higher terrain. Look for temps inland to be 5 to 10 degrees below normal through Saturday, with Thursday the coolest day. Tolleson .LONG TERM...(Saturday Night through Wednesday)...The models continue to indicate that the main long wave ridge position will remain well offshore out near 150w or so during this period, with northwest flow aloft across the Pacific Northwest into the persistent long wave trough position across the western U.S. This results in continued below normal temps, and possibly a few showers at times. Timing is a bit uncertain, but a few showers are possibly Sunday especially around the northern higher terrain, and around Tuesday and Wednesday. No hot weather on the immediate horizon, through at least the next 10 days. Tolleson && .AVIATION...Widespread MVFR cigs and scattered precipitation continue this afternoon across the region as a weak frontal boundary continues to slowly advance from west to east across the area. Local pockets of IFR cigs continue, and heavier rain may occasionally reduce visibilities. Slight trend of improvement to VFR cigs possible later this afternoon into early afternoon from west to east, particularly across the northern portions of the area where the front and associated clouds/rain have pushed ahead. For the coast, areas that clear behind the back edge of frontal cloud band may see fog or low stratus develop given moist lower levels and light wind. Another front will bring more rain and lowering cigs again Thursday afternoon. KPDX AND APPROACHES...MVFR cigs continue this evening with scattered showers around. Showers decrease this evening and cigs may improve to VFR for a short time, but likely lower to MVFR again overnight through early tomorrow. Cullen && .MARINE...Cold front near the coast will continue onshore this morning. Southerly winds are generally in the 10 to 15 kt today, with seas remaining choppy and dominated by short period waves. Winds will vary between south and southwest for the remainder of the week. The next front nears the waters late Thursday, bringing increasing gusts to near advisory strength. Then, stronger north winds return late in the weekend as high pressure rebuilds over the northeastern Pacific. Seas will remain 4 to 6 feet through much of the week but conditions remain confused with a mix of a short period west-northwest swell, choppy south wind wave/fresh swell, and a small but longer period south swell also occasionally appearing in spectral observations at times. Cullen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
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